1. Technical Field
The present invention generally relates to tonneau cover assemblies for the cargo areas of automotive vehicles and, more particularly, to a tonneau cover assembly having a self-adjusting adjusting mechanism for accommodating dimensional changes of a tonneau cover due to temperature variations.
2. Discussion
Many modern automotive vehicles are provided with an open cargo storage compartment for storing and transporting bulky goods. One such cargo storage compartment is the bed portion of a pickup truck. In order to protect the goods within the pickup truck bed from exposure or damage from the elements, and to improve wind resistance and thus fuel economy, many pickup truck beds are covered with tonneau cover assemblies.
Typical tonneau cover assemblies include a frame consisting of a plurality of rails mounted to the top of the pickup truck bed walls. A fabric cover is then removably mounted to the frame assembly rails so as to cover the open portion of the bed. While such assemblies generally function very well, there are some drawbacks to conventional assemblies.
For example, the fabric covers commonly employed in such conventional tonneau cover assemblies have a tendency to shrink and expand with ambient temperature variations. At room temperature, for example 68-72.degree. Fahrenheit, the tonneau cover snaps onto the frame assembly rails with minimal effort and yields a taut cover. However, tonneau covers commonly shrink when ambient temperatures decrease. The shrinking cover tends to pull up from the corners of the assembly. Even more detrimental, it is sometimes extremely difficult to pull the cover into the proper position for snapping it onto the frame assembly after the cover has been removed from the frame assembly and then experiences shrinkage due to temperature drop. Further, the tonneau cover may expand when it is exposed to high ambient temperatures. This tends to wrinkle the cover which may lead to flapping during transportation.
A few prior art approaches have been proposed for accommodating the dimensional variations of tonneau covers due to temperature changes. One approach includes the provision of spacers between the frame rails. By taking the rails apart, inserting a spacer, and reconnecting the rails, a larger frame rail assembly is provided. However, such spacers are extremely burdensome and are commonly unused. Further, such spacers do not accommodate cover shrinkage.
Another approach includes the provision of snap corners between the assembly rails. Each snap corner includes a tab that may be extended from a stowed position to provide an extended anchoring site for the cover. Unfortunately, such tabs are often unused and are prone to breakage. Further, such tabs do not accommodate cover shrinkage.
Yet another approach is to provide a ratcheting mechanism for moving the rails of the assembly relative to one another. To move the rails relative to one another, the ratcheting mechanism is manually adjusted. This forces the rails apart or draws then nearer. However, such manual ratcheting mechanisms commonly go unused and are prone to malfunction. Further, such ratcheting mechanisms are difficult to operate and often require separate tools.
In view of the foregoing, it would be desirable to provide a automatic mechanism for adjusting a tonneau cover frame assembly to accommodate dimensional changes of a tonneau cover due to temperature variations.